Low-temperature transformations of sodium sulfate and sodium selenite in the presence of pre-reduced palladium modifier in graphite furnaces for electrothermal atomic absorption spectrometry |
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| Institution: | 1. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Kosygin str. 19, Moscow, 117975 Russia;2. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky pr. 47, Moscow, 117334 Russia;3. UFZ Centre for Environmental Research Leipzig-Halle, Department of Analytical Chemistry, Permoserstrasse 15, D-04318 Leipzig, Germany;1. National Key Lab of Superhard Materials, Jilin University, Changchun 130012, China;2. Department of Physics and Chemistry, Heihe University, Heihe 164300, China;1. Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA;2. Department of Immunology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA;3. Department of Biomedical Research, National Jewish Health, Denver, Colorado, USA;1. School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, China;2. Guangzhou Fiber Product Testing Institute, Guangzhou 510220, China |
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| Abstract: | The low-temperature interaction (up to 550°C) of a pre-reduced palladium modifier with sodium sulfate and sodium selenite on the pyrolytic graphite platform was studied using X-ray photoelectron spectroscopy (XPS) and electron microprobe analysis. The equipment applied allowed the introduction of samples heated in an argon flow into the analytical chamber of the XPS spectrometer without contact with the air. Electron microprobe analysis showed that palladium and sulfur preferably occupy different areas on the platform surface. On the contrary, selenium from sodium selenite tends to occupy areas of the graphite surface covered with palladium. The most probable reason for this is the chemisorption of selenium (IV) on the palladium surface at the drying stage. No changes in the XPS spectra of metallic Pd and S6+ were observed when Na2SO4 and Pd were heated together on the graphite platform in the range 100–550°C. The reduction of sodium selenite on the graphite surface already starts during drying. Pre-reduced palladium intensifies this process. The rate of the reduction is proportional to the amount of palladium, and in the presence of palladium at an atomic ratio of Pd/Se=7.5, the transformation of Se4+ into Se0 completes at 250°C. |
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